No. 404.] HABITS OF THE BROOK LAMPREY. 619 
We do not think the lampreys have any definite method in 
the construction of their nests. When they seize a stone they 
usually endeavor to carry it straight ahead, without other in- 
stinct apparently than to remove it from the nest, no matter in 
what direction they may be heading. Often, however, they 
allow themselves to be carried down stream by the current, 
together with the stones which they have seized. A lamprey 
has been seen to carry a stone up stream a short distance and 
then allow itself to drift back again with it. In a few cases 
they have been observed to carry stones into the nest from 
without. They cling very persistently to whatever object they 
may have attached themselves, on one occasion a lamprey per- 
mitting itself to be lifted from the water attached to the boot 
of one of the writers. Contrary to the observation of Gage 
and Dean and Sumner, we have noted two lampreys move a 
stone conjointly. The largest stone moved (only an inch, how- 
ever) by a single lamprey weighed thirty-three grams. In 
moving stones the lamprey arches its back and employs power- 
ful brush-like movements of the tail against the stream bed, as j 
in spawning. As noted by Dean and Sumner, one lamprey will 
frequently seize another and pull it away from its place of 
attachment. It is very interesting to watch them do this. 
One seizes another by the head and shakes it as a dog would a 
rat. In so doing they are usually carried out of the nest by 
the current, holding to each other for a short distance, when 
they separate and return to the nest. 
The size of nests and depth of stream over them is ex- 
pressed by the following data, which are the average for 
twenty-six nests. 
DIAMETER || ro CURRENT. DIAMETER | TO CURRENT. DEPTH oF STREAM. 
7i inches 7i inches 15 inches! 
There is considerable variation both in the form and situa- 
tion of the nests. The longer diameter may be either parallel 
or perpendicular to the current. They may be situated in any 
! Average for twenty-five nests. 
